A compound of formula IIa: ** Formula ** or a pharmaceutically acceptable salt thereof, in which: X is carbon or nitrogen； Y is carbon or nitrogen； R1a is hydrogen, halogen, nitro, cyano, hydroxy, (C1-C6) alkyl, (C1-C6) alkenyl, (C1-C6) alkynyl, (C1-C6) alkoxy, aryl, heteroaryl, cycloalkyl, heterocyclyl, arylalkyl ( C1-C3), heteroarylalkyl (C1-C3), cycloalkylalkyl (C1-C3), heterocyclylalkyl (C1-C3), hydroxyalkyl (C1-C3), N (R5a) 2, C (>； = NOH) NH2, NR5aCON (R5a ) 2, CON (R5a) 2, CO2R5a, COR6a, OC (O) R5a, SO2N (R5a) 2, SO2R6a, NR5aCOR6a, NR5aCO2R6a, NR5aSO2R6a or OC (>； = O) N (R5a) 2, each optionally substituted with one or more groups represented by R4a； R2a is (C1-C6) alkyl, (C1-C6) alkoxy, S-C1-C6 alkyl, SO-C1-C6 alkyl or SO2-C1-C6 alkyl, optionally substituted with one or more groups represented by R4a； R3a is halogen, (C1-C6) alkyl or (C1-C6) alkoxy, each optionally substituted with one or more groups represented by R4a； each R4a is independently halogen, nitro, cyano, hydroxy, (C1-C4) alkyl, halo (C1-C3) alkyl, hydroxyalkyl (C1-C4), alkoxy (C1-C4), haloalkoxy (C1-C4), aryl, haloaryl , cycloalkyl, arylalkyl (C1-C3), arylalkoxy (C1-C4), heterocyclyl, N (R5a) 2, C (>； = NOH) NH2, NR5aCON (R5a) 2, CON (R5a) 2, CO2R5a, COR6a, OC (O) R5a, SO2N (R5a) 2, SO2R6a, SR6a, S-(C1-C3) alkylcycloalkyl, NR5aCOR6a, NR5CO2R6a, NR5aSO2R6a, S (>； = O) R6a, -Ocycloalkyl, -O-heterocyclyl, ada OC (>； = O) N (R5a) 2, each R5a is independently hydrogen, (C1-C10) alkyl, aryl or aryl (C1-C6) alkyl, each optionally substituted with halogen, (C1-C3) alkoxy, alkyl ( C1-C3), haloalkyl (C1-C3), haloalkoxy (C1-C3), cyano or nitro； and each R6a is independently hydrogen, halogen, (C1-C10) alkyl, (C1-C10) alkoxy, (C1-C3) arylalkyl, cycloalkyl or (C1-C3) alkoxy, each optionally substituted with halogen, (C1-) alkoxy C3), (C1-C3) alkyl, (C1-C3) haloalkyl, (C1-C3) haloalkoxy, cyano or nitro.Un compuesto de fórmula IIa:**Fórmula** o una sal farmacéuticamente aceptable del mismo, en la qu
